Wheel speed sensor

ABSTRACT

A self-adjusting wheel speed sensor mechanism including a magnetic sensor and rotor on a vehicle axle and wheel. The sensor and rotor are automatically adjusted to a predetermined relationship as the wheel is mounted on the axle and are maintained in that relationship during operation of the vehicle.

United States Patent Fiteny et al. Nov. 20, 1973 WHEEL SPEED SENSOR [56] References Cited [75] Inventors: Louis M. Fiteny, Dearborn Heights; UNITED STATES P T S Leo G. Oehring, Wyandotte, both of 3,487,247 12/1969 Scheffler 310/168 Mich. [73] Assignee: Rockwell International Corporation, Primary Examiner D' Duggan Pittsburgh Pa. Att0rney-John R. Bronaugh et al.

[22] Filed: June 16, 1972 57 ABSTRACT [21] Appl. No.: 263,686 A self-adjusting wheel speed sensor mechanism including a magnetic sensor and rotor on a vehicle axle and wheel The sensor and rotor are automatically adg justed to a predetermined relationship as the wheel is I mounted on the axle and are maintained in that rela [58] Field of Search 310/168, 155, 169, d f h l 31O/152 tions 1p unng operation 0 t e ve 10 e.

11 Claims, 4 Drawing Figures WHEEL SPEED SENSOR BACKGROUND OF THE INVENTION Modern anti-skid control systems operate in response to electrical signals indicative of the angular velocity of one or more of the vehicle wheels. Usually these signals are derived from an electromagnetic sensor, including a magnet carried by a stationary portion of the vehicle such as the axle housing and a toothed or notched metal ring which rotates with the wheel opposite the magnet. As the ring teeth pass the magnetic sensor device, the resulting variations in flux produce a signal, the frequency of which is a function of the angular velocity of the wheel.

To produce the required accuracy of the velocity signal, the sensor and ring must be precisely located with respect to each other during assembly of the wheel on the axle, and must remain in a preselected relationship even after extended operation in which the components are subjected to road shocks and constant vibration.

It is also essential that installation of the sensor mechanism be accomplished in a manner adaptable to mass production methods to minimize the need for skilled technicians and elaborate installation techniques. In addition, the velocity sensing unit must be protected against dirt, mechanical damage and heat.

SUMMARY OF THE INVENTION Accordingly, the primary object of this invention resides in the provision of a novel, self-adjusting, vehicle wheel speed sensor mechanism in which the rotating and stationary components of the mechanism are automatically adjusted to a predetermined precise relationship as the wheel is mounted on an axle and maintained in that predetermined relationship during operation of the vehicle.

Another object of the invention resides in the provision ofa novel, self-adjusting wheel speed sensor mechanism which facilitates low cost installation of the sensor components and assures that the components are positioned and maintained in proper predetermined relationship to produce an accurate velocity signal.

A further object of the invention resides in the provision of a novel, self-adjusting wheel speed sensing mechanism in which the stationary and rotating sensing components are separately mounted on an axle and a wheel, automatically adjusted to a precise predetermined relationship as the wheel is mounted on the axle, and maintained in that predetermined relationship during operation of the vehicle. Consequently, the sensing components may be quickly and easily mounted on the axle and wheel, and the wheel may be rapidly installed on the axle by unskilled technicians employing routine installation techniques.

The novel wheel speed sensing mechanism of the invention attains these and other objects by providing a rotor component which rotates with the wheel and a magnetic sensor component mounted on the axle against rotation. The sensor component is mounted for free floating, inward axial movement so that as the wheel is placed on the axle a radial face of the rotor component engages the opposing radial face of the sensor component to automatically shift and adjust the sensor component axially inwardly to a precise predetermined relative operating position so that an accurate velocity signal is produced. The engaging radial face of one of the components is coated with a dielectric material which initially automatically establishes a predetermined gap between the rotor and the sensor, and this gap is maintained during operation by locking the sensor against outboard axial movement. A plurality of springs exert an outboard biasing force on the sensor to prevent inward walking of the sensor caused by road shocks and vibrations.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a fragmentary section showing a wheel sensor mechanism constructed in accordance with the present invention;

FIG. 2 is a fragmentary section taken generally along line 22 of FIG. 1 and illustrating the sensor unit which is mounted on the axle;

FIG. 3 is a schematic plan view of the sensor unit taken generally along line 3-3 of FIG. 2; and

FIG. 4 is a fragmentary section taken generally along line 44 of FIG. 1 and illustrating the rotor component which is mounted on the wheel.

DETAILED DESCRIPTION OF THE INVENTION For present purposes the invention will be disclosed as applied to a non-steerable vehicle axle, such as a trailer axle designed for heavy duty use. As used herein, and in the claims, the term axle is intended to refer to any stationary component on which a wheel hub is mounted and includes components commonly referred to as spindles or hollow tubular housings which accommodate drive shafts if the wheels are to be driven.

Referring to the drawings, axle 10 is provided at its outer end with a bearing seat for bearing assembly 12 upon which wheel hub 14 is rotatably supported in the usual fashion. Brake drum 16 is connected by a plurality of bolts 18 to a radial flange 20 of hub 14, with flange 20 also carrying a plurality of wheel mounting studs which are not shown. The brake assembly is conventional and includes brake shoes 22 carrying linings 24 and a brake operating mechanism including an actuating arm which is schematically shown at 26 and is connected to a spider having a flange section 28 secured on axle l0.

Bearing assembly 12 may be provided with lubricant from a cavity located adjacent its outer end and the inner end of the assembly will be sealed by a seal unit (not shown) carried between the wheel hub and axle.

The wheel speed sensor assembly 30 includes a rotor component formed by a steel ring 32 carried by a flared ring 34 and bolts 18 on the wheel hub flange 20. On its inboard radial face, ring 32 has a plurality of equally circumferentially spaced teeth 36 and notches 38 therebetween. In a typical case, ring 32 will have an CD. of 8.5 inches and will be provided with equally spaced teeth 36 having a radial length of approximately 0.75 inches and a depth of approximately 0.125 inches.

Sensing assembly 30 also includes a magnetic sensor unit 40 which is of arcuate configuration and is formed on the same radius as the ring 30 and in a typical case may have a radial width of approximately one inch. Unit 40 includes a magnet assembly, which may be of conventional construction, typically has three poles-42 embedded in a plastic body portion 44 and a second housing portion 46 containing electric components (not shown) which convert the signals generated by the magnets to a proper form for use in the brake control system. The leads to the power supply for the sensor unit 40 as well as for the output signal are contained in a cable 48 leading into one end of the unit.

The outboard faces of sensor portions 44 and 46 are coated by gap pads 50 and 51, formed of a dielectric material such as an epoxy. As described hereinafter, pads 50 and 51 establish a predetermined axial gap or clearance between the ring teeth 36 and poles 42 of the sensor unit. For example, the thickness of the pads covering poles 42 may be 0.060 inches.

As shown in FIG. 1, sensor unit 40 is protectively enclosed in an arcuate, channel-shaped shield 52 and is mounted for inward axial shiftable movement by a plurality of pins 54 which are axially movable inwardly in bosses 55 formed on a bracket assembly 56 suitably fixed to the spider 28. Each of the pins 54 is biased in the outboard direction by a spring 58 located within boss 55. Unit 40 and shield 52 are fixed on pins 54 between the pin collars 60 and a plurality of threaded nuts 62 received within recesses 64 in the outboard radial face of the unit.

Although pins 54 are movable axially inwardly on bracket assembly 56, each of the pins is prevented from moving outwardly by a one-way clutch or lock ring 66 which permits inward but not outward movement of the pin. Each ring 66 is held in place around the pins by cap 68 threaded on the boss 55.

Proper operation of the wheel sensing assembly 30 is obtained only if the sensor unit 40 is precisely located and maintained with respect to the ring 32 so that a predetermined axial clearance or gap is provided between teeth 36 and magnet poles 42. This gap is automatically obtained and maintained by the described sensor assembly and its mounting arrangement.

Before assembling the wheel parts, bracket 56 will be fixed on axle l and sensor unit 40 and mounting pins 54 will be mounted on the bracket with unit 40 located in its outermost outboard position. The outboard radial faces of gap pads 50 and 51 will be in a plane substantially perpendicular to the axis of axle 10.

Similarly, ring 34 will be connected to flange 20 of wheel hub 14 so that ring teeth 36 will be in a radial plane substantially parallel to the radial faces of pads 50 and 51.

As wheel hub 14 is placed on axle 10, teeth 36 will engage the opposed radial faces of gap pads 50 and 51 and will displace unit 40 and pins 54 axially inwardly against the force of compressed springs 58. When the hub is fully tightened on the axle in the position shown in FIG. 1, magnets 42 of unit 40 and teeth 36 will be precisely located with respect to each other and spaced a predetermined axial distance established by the thickness of gap pads 50 and 51. This precise relationship is maintained during operation of the vehicle by the clutch rings 66 which lock pins 54 against outward movement. Thus, even though there may be some wear of gap pads 50 and 51 caused by rotating teeth 36, the predetermined gap or clearance between the teeth and magnetic poles 42 remains fixed because unit 40 is locked against outboard movement.

It is clear that, due to the self-adjusting characteristics of sensor unit 40, installation of wheel hub 14 on axle is readily facilitated since the precise clearance gap between the rotor teeth and sensor unit required for proper operation of the system is automatically obtained and maintained.

Following removal of wheel hub 14 and before reassembly of the hub on axle 10, it is necessary to remove caps 68 from bosses 55 and readjust the position of clutch rings 66 on pins 54 so that sensor unit 40 may be relocated in its outermost outboard position. Consequently, as the wheel hub is reassembled on the axle, sensor unit 40 and teeth 36 are again automatically adjusted to the desired predetermined relationship.

During operation of the vehicle the sensor components are subjected to road shocks and constant vibration which may tend to displace unit 40 inwardly. However, the compressed springs 58 exert a sufficient force against pins 54 to counteract the shock and vibration forces and thereby maintain the precise predetermined relationship between poles 42 and teeth 36 required for proper operation.

The sensor unit 40 is effectively shielded against heat and mechanical damage by the channel-shaped shield member 52, and also by annular retainer 34 by which ring 32 is mounted on the wheel hub. Ring 34 may also act as a slinger ring which directs any excess oil that may leak past the seal of the bearing assembly 12 to one or more drain openings 70 which extend through the hub 14.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiment is therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meansing and range of equivalency of the claims are therefore intended to be embraced therein.

What is claimed and desired to be secured by Letters Patent is:

1. A wheel speed sensor assembly for installation in association with a wheel rotatably mounted on an axle comprising a ring member having discontinuities on one radial face, said ring member being adapted to be connected to said wheel for rotation therewith with said discontinuities facing axially inwardly, a magnetic sensing assembly, mounting means operatively securing said magnetic sensing assembly on said axle and permitting axial movement of said sensing assembly inwardly while preventing axial movement of said sensing assembly outwardly whereby said sensing assembly is automatically adjusted in predetermined relationship with said radial face of said ring in response to axial movement of said ring inwardly, said mounting means including bracket means connected to said axle, at least one mounting pin connected to said sensing assembly and axially slidably mounted on said bracket means, said retaining means permitting inward axial movement of said pin but preventing outward axial movement thereof.

2. The assembly as defined in claim 1, said mounting means including spring means for biasing said sensing assembly in an outward axial direction.

3. The assembly as defined in claim 1, comprising spring means on said bracket means for biasing said sensing assembly in an outward axial direction.

4. The assembly as defined in claim 1, said retaining means comprising a one-way clutch element associated with said pin.

5. The assembly as defined in claim 1, wherein a layer of dielectric material is provided on at least a portion of the radial surface of said sensing assembly which faces said one radial face of said ring member, said layer of dielectric material being engaged by said one radial face of said ring member when the wheel is mounted on the axle.

6. The assembly as defined in claim 1, comprising stationary shield means positioned adjacent to said sensing assembly.

7. The assembly as defined in claim 1, comprising annular retainer means for connecting ring member to said wheel.

8. The assembly as defined in claim 1, said mounting means including spring means for biasing said sensing assembly in an outward axial direction, and said retainer means including one-way clutch means which permits inward axial movement of said sensing assembly but prevents outward axial movement thereof.

9. A wheel speed sensor assembly for installation in association with a wheel rotatably mounted on an axle comprising a ring member having discontinuities on one radial face and being adapted to be connected to said wheel for rotation therewith with said discontinuities facing axially inwardly, a self-adjusting magnetic sensing assembly, means for mounting said magnetic sensing assembly on said axle, said mounting means including bracket means connected to said axle, at least one mounting pin connected to said sensing assembly and axially slidably mounted on said bracket means, retaining means permitting inward axial movement of said pin but preventing outward axial movement thereof, spring means on said bracket means for biasing said sensing assembly in an outward axial direction, and a layer of dielectric material on at least a portion of the radial surface of said sensing assembly which faces said one radial face of said ring member, said layer of dielectric material being engaged by said one radial face of said ring member to cause said sensing assembly to be automatically axially adjusted in response to axial movement inwardly of said ring member.

10. The assembly as defined in claim 9, said retaining means comprising a one-way clutch element associated with said pin.

11. The assembly as defined in claim 9, comprising shield means positioned adjacent said sensing assembly. 

1. A wheel speed sensor assembly for installation in association with a wheel rotatably mounted on an axle comprising a ring member having discontinuities on one radial face, said ring member being adapted to be connected to said wheel for rotation therewith with said discontinuities facing axially inwardly, a magnetic sensing assembly, mounting means operatively securing said magnetic sensing assembly on said axle and permitting axial movement of said sensing assembly inwardly while preventing axial movement of said sensing assembly outwardly whereby said sensing assembly is automatically adjusted in predetermined relationship with said radial face of said ring in response to axial movement of said ring inwardly, said mounting means including bracket means connected to said axle, at least one mounting pin connected to said sensing assembly and axially slidably mounted on said bracket means, said retaining means permitting inward axial movement of said pin but preventing outward axial movement thereof.
 2. The assembly as defined in claim 1, said mounting means including spring means for biasing said sensing assembly in an outward axial direction.
 3. The assembly as defined in claim 1, comprising spring means on said bracket means for biasing said sensing assembly in an outward axial direction.
 4. The assembly as defined in claim 1, said retaining means comprising a one-way clutch element associated with said pin.
 5. The assembly as defined in claim 1, wherein a layer of dielectric material is provided on at least a portion of the radial surface of said sensing assembly which faces said one radial face of said ring member, said layer of dielectric material being engaged by said one radial face of said ring member when the wheel is mounted on the axle.
 6. The assembly as defined in claim 1, comprising stationary shield means positioned adjacent to said sensing assembly.
 7. The assembly as defined in claim 1, comprising annular retainer means for connecting ring member to said wheel.
 8. The assembly as defined in claim 1, said mounting means including spring means for biasing said sensing assembly in an outward axial direction, and said retainer means including one-way clutch means which permits inward axial movement of said sensing assembly but prevents outward axial movement thereof.
 9. A wheel speed sensor assembly for installation in association with a wheel rotatably mounted on an axle comprising a ring member having discontinuities on one radial face and being adapted to be connected to said wheel for rotation therewith with said discontinuities facing axially inwardly, a self-adjusting magnetic sensing assembly, means for mounting said magnetic sensing assembly on said axle, said mounting means including bracket means connected to said axle, at least one mounting pin connected to said sensing assembly and axially slidably mounted on said bracket means, retaining means permitting inward axial movement of said pin but preventing outward axial movement thereof, spring means on said bracket means for biasing said sensing assembly in an outward axial direction, and a layer of dielectric material on at least a portion of the radial surface of said sensing assembly which faces said one radial face of said ring member, said layer of dielectric material being engaged by said one radial face of said ring member to cause said sensing assembly to be automatically axially adjusted in response to axial movement inwardly of said ring member.
 10. The assembly as defined in claim 9, said retaining means comprising a one-way clutch Element associated with said pin.
 11. The assembly as defined in claim 9, comprising shield means positioned adjacent said sensing assembly. 